Catheters are long, thin, flexible tubes of plastics material that can be inserted into a blood vessel or other body cavity for introducing or removing fluids, either liquids or gases. They are used by medical personnel as a matter of routine. Catheters can vary widely in size, depending upon the application: from about 0.1 mm internal diameter for use with premature babies, up to more than 5 mm internal diameter for use with adults. They often have measurement markings provided along their length, the markings serving as a guide to the depth of insertion into the patient's body.
Premature infants, or term infants requiring resuscitation measures, invariably require the ongoing administration of drugs and fluids. Moreover, frequent blood samples must be taken to monitor the infant's progress, bearing in mind that infants can deteriorate very rapidly if things go wrong without being detected promptly. Clearly, therefore, it is vital that good venous/arterial access is achieved and maintained.
Venous/arterial access through peripheral access sites such as the arms, legs or scalp is to be avoided if at all possible. As infant patients can be so small, it is desirable to avoid puncturing their blood vessels even if suitable blood vessels can be found: peripheral access is usually very limited. Moreover, serious injury can ensue when administering certain drugs or fluids peripherally, ranging from superficial tissue damage to permanent disfigurement. Plastic surgery may be required for these peripheral injuries and, in later life, orthopaedic intervention may be required to treat damaged joints.
Conversely, the venous and arterial vessels found within the normal anatomy of an umbilical cord (i.e. at the umbilical stump or umbilicus) provide ready access to a infant's bloodstream and so are favoured over peripheral access sites. Accordingly, for those babies admitted to a neo-natal intensive care unit and unless complications arise which inhibit use of the umbilicus, the usual practice is to site small diameter umbilical catheters (also known as lines) in the umbilicus as soon as possible after birth. Once in situ, these lines readily allow fluids including transfusions and drugs to be administered and blood samples to be taken.
When locating a line inside an infant's body, a nurse or doctor has to be careful to place the line in a position that least compromises the dynamics of the cardiovascular system. This is a trial-and-error process, involving an attempt at correct positioning followed by an X-ray to confirm the actual position of the end of the line. At that stage, if the line is found to extend beyond its target position, it can be pulled back. On the other hand, if the line falls short of the target, the risk of introducing infection means that the line is never inserted any deeper. Instead, the original line is withdrawn and discarded and a sterile replacement line is sited: the positioning procedure begins all over again.
Clearly, once a line is in an acceptable position after this intricate positioning procedure, it is essential that the line is securely anchored to avoid any accidental displacement with respect to the infant's umbilicus. The line may need to be in place for a period of weeks: the longer a line remains undisturbed in situ in accordance with planned treatment, the lower the risk of harm to the patient. With premature infants in particular, lines are essential: if access via them is lost, the risk of a poor outcome or even death is notably higher. Dislodgement of a line is most undesirable because reinsertion not only increases the risk of introducing infection, but also is difficult to achieve because the anatomy of the umbilicus naturally becomes distorted and/or tends to close up tightly a few days after birth.
The current and long-standing line-anchoring practice is to suture the line directly to the umbilicus and then to construct a securing bridge from medical adhesive tape applied to the abdomen. This adhesive tape bridge takes the stress of axial loads on the line at points spaced from the umbilicus, thereby minimising disturbance to the umbilicus.
In a common construction illustrated in FIG. 1, an adhesive tape bridge 10 is made from a total of six strips of medical adhesive tape. Two pairs of strips are adhesively secured to the baby's abdomen 11 one each side of, and spaced from, the umbilicus 12. Each pair is shaped into an inverted V and the pairs are mutually parallel with their apices aligned with the umbilicus, creating upstanding supports. The remaining two strips of tape are applied face-to-face about the line 13 and their ends are attached to the apices of the supports, thus bridging the gap between the supports and gripping the line 13. Alternatively, the strips of adhesive tape gripping the line 13 may be sutured to the baby's abdomen 11, avoiding sticking extra strips of adhesive tape to the abdomen.
The adhesive tape bridge is cheap and simple but suffers a number of problems. Perhaps most seriously, and no matter how carefully an adhesive tape bridge is constructed, the adhesive will deteriorate over time. The bridge may ultimately fall apart or otherwise fail to grip the line, thus presenting a danger of the line being displaced. Clearly, this risk increases the longer an adhesive tape bridge is relied upon: it must be inspected frequently and if necessary renewed. Of course, inspection and renewal are operations that can themselves disturb the line.
If an adhesive tape bridge fails to grip a line, the line can be pulled out or otherwise displaced from its ideal location by movements of the infant, as well as by disturbances when medical personnel carry out clinical procedures on the infant such as re-intubation, taking samples, changing nappies/diapers, cleaning and so on. Paradoxically, any disturbance of the line can be hidden by the bulky adhesive tape bridge and so escape detection, especially as more tape may have been added over time to repair damage to the bridge. Wholly unnecessary death or disability is the all too frequent result.
The infant's movements and the disturbance of clinical procedures can, of course, also contribute to the deterioration of the adhesive tape bridge. However, the main factor in deterioration stems from the fact that a premature infant's skin is immature, undeveloped and hence very permeable. Coupled with an infant's large surface area to weight ratio, this leaves the infant liable to dehydration. This is the reason why premature infants are kept in a humidified atmosphere within incubators or bubble coverings. Over time, the moisture promoted by these humid surroundings can weaken the bonds that hold together an adhesive tape bridge and that hold the bridge in place on an infant's skin.
Other disadvantages of the adhesive tape bridge are that adhesive contact with a premature infant's abdomen could damage the infant's extremely fragile and sensitive skin, and that its construction takes valuable time.
Some of the shortcomings of adhesive tape bridges are addressed in U.S. Pat. No. 5,370,627 to Conway. Conway discloses a catheter securing bridge that consists of an annular base having a central aperture and two semi-circular flaps pivotally connected to the base. The underside of the base is coated with an adhesive layer, as are the opposing faces of the flaps.
In use, the base is adhesively secured to the infant so that it encircles the umbilicus which is thus presented in the middle of the aperture. Next, the catheter is introduced into the umbilicus, and once properly located is sutured in place on the umbilicus. The flaps are lifted up towards one another so that they extend upwardly from the base and are then adhesively secured together, trapping a portion of the projecting catheter.
Whilst Conway's catheter securing bridge represents an improvement over the conventional adhesive tape bridge in terms of convenience of application, it is apparent that Conway has taken the adhesive tape bridge as a starting point. Conway's device therefore shares many of the problems suffered by the adhesive tape bridge: in particular, it will eventually work loose and will therefore allow the catheter to become displaced, and it can damage the patient's skin by virtue of adhesive contact.
Neonatal care requires exceptional precision but, of course, it is not the only medical or surgical field that requires reliable and convenient location of a catheter. Intravenous drips, chest and abscess drains and urethral catheters, are merely examples of many other applications that would benefit from better fasteners.
Analogous problems are experienced in fastening an endotracheal tube used to ventilate a patient: see FIG. 2. When intubating the patient 14, the endotracheal tube 15 is passed through a plastics grip or, as illustrated, a silicone rubber collar 16 held on the patient's mouth by a net or stocking hat and ribbon ties as shown that pass through holes 17 in the collar 16, and is fixed to the collar 16 by a cable tie 18 or suture (not shown). The patient 14 is then x-rayed to ensure that the end of the endotracheal tube 15 is correctly positioned just above the bifurcation of the trachea, i.e. the point where the trachea branches into the bronchi. If the endotracheal tube 15 is not correctly positioned—and adjustment is usually required—the cable tie 18 or suture must be removed, the tube 15 pulled out or pushed in (the risk of infection is acceptable in this instance because the trachea is always exposed to the environment), the cable tie 18 or suture must be re-affixed and then another x-ray must be performed to confirm correct positioning. Repeated removal and replacement of the cable tie 18 or suture takes time, costs money and generally militates against correct positioning of the endotracheal tube 15.
It is essential that the endotracheal tube is accurately positioned so as to avoid injury at the bifurcation of the trachea or inadvertent ventilation of only one side of the chest, usually the right side because the right bronchus is anatomically more vertical compared to the left bronchus.
In general, the problems of fastening lines and other articles to a patient are well known and have been addressed by numerous inventors. Examples of recent thinking are U.S. Pat. Nos. 5,152,298 to Kreyenhagen et al, 5,257,975 to Foshee, and 5,662,616 to Bousquet.
Kreyenhagen et al discloses an implantable suture sleeve for anchoring the lead body of an implantable medical device, such as a cardiac pacemaker, to a patient's body tissue such as a vein and/or a muscle within the chest cavity. The sleeve includes an elongated externally threaded tubular member having a lumen for receiving the lead body and an internally-threaded collar that is threaded onto the external thread of the tubular member. The tubular member and the collar have engaging tapered surfaces so that, when the collar is tightened, a soft insert within the tubular member is compressed into gripping engagement with the lead body.
As the suture sleeve of Kreyenhagen et al is designed for implantation, it is clearly intended for once-only operation. Further, as a result of its specialised purpose, the suture sleeve is unnecessarily bulky, expensive and complex, both in its design and its operation, for the more general purposes of the present invention. It will also be noted that the suture sleeve exerts its inward compressive force on the lead body about a narrow annular ridge or band and so is designed to crush the lead body to a limited extent. It is noted that crushing is not appropriate for a tubular lines as this would restrict its lumen. It is also noted that the facility for limiting the extent of crushing requires the further complication of cooperable surfaces on the tubular member and the collar.
Foshee discloses a cannula retention device actuable in a single operation to secure a cannula above and below a patient's body wall. The embodiments disclosed include a tubular sleeve which is slit either longitudinally or, preferably, spirally. The sleeve is secured to the distal end of the cannula while being mounted loosely over the cannula at the proximal end. Longitudinally compressing or twisting the sleeve, as appropriate, makes the slit tubing expand above and below the body wall to secure the cannula.
It will be noted that the means of location disclosed in Foshee requires modification to the article to be attached to the patient, in this case a cannula, and would be of no use in attaching an article at points of attachment outside the body wall.
Bousquet was published after the priority date of the present invention and discloses a transcutaneous access device including a subcutaneous skirt, a transcutaneous neck and an extracutaneous bellows-like extendible sleeve. The device functions as a conduit for an access catheter and is sized to minimise contact with the catheter. The aim is to allow motion of the catheter relative to the implanted portions of the access device so that the patient's body motion does not break the biological seal that forms around the access device. Allowing motion of, and avoiding contact with, the catheter in this way is contrary to the aims of the present invention.